#include<fstream>
#include<vector>
#include<cstring>
using namespace std;

ifstream cin("ctc.in");
ofstream cout("ctc.out");

const int NMAX = 1e5+1;

vector<int> v[NMAX], inv[NMAX], st, comp[NMAX];
int n, m;
bool marked[NMAX];

void dfs(int nod, vector<int>& st, vector<int>* graph)
{
    marked[nod] = 1;
    for(int vecin : graph[nod])
        if(!marked[vecin])
            dfs(vecin, st, graph);

    st.push_back(nod);
}

int main()
{
    cin>>n>>m;
    for(int i=1; i<=m; i++)
    {
        int x, y;
        cin>>x>>y;
        v[x].push_back(y);
        inv[y].push_back(x);
    }

    for(int i=1; i<=n; i++)
        if(!marked[i])
            dfs(i, st, v);

    memset(marked, false, sizeof(marked));

    int nr = 0;
    while(st.size())
    {
        int i = st.back();
        st.pop_back();
        if(!marked[i])
        {
            nr++;
            dfs(i, comp[nr], inv);
        }
    }
    cout<<nr<<"\n";
    for(int i=1; i<=nr; i++)
    {
        for(int nod : comp[i])
            cout<<nod<<" ";
        cout<<'\n';
    }
    return 0;
}